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What is the acceleration due to gravity on Roshar?


Hoiditthroughthegrapevine

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3 hours ago, RShara said:

This post by jofwu should have everything you need for your calculations

 

 

This makes me think. The size of roshar continent is roughly that of asia, and the distance between shinovar and alethkar roughly the one between europe and china. So maybe there was on roshar a Cristopherin Chiken who, after miscalculating the distance involved, attempted to reach alethkar from shinovar sailing westward.

there was no continent to discover, and he sunk in a highstorm anyway.

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Gravitational acceleration isn't directly proportional, I don't think?  So .7 Earth Gravity wouldn't necessarily be 70% of 9.8 m/s^2.  I can't remember for sure.  Anyway, the post above gives the mass of Roshar, which will allow him to calculate the correct gravitational acceleration.

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Awesome, thanks all!

Thanks for dumping @Jofwu's calculations of the physical characteristics of Roshar @RShara, really helpful stuff.

I am working on some calculations for conjoined fabrials. I realized that after the first couple of answers came in that the proportional gravity of Roshar was stated by Khriss in Arcanum Unbounded (duh), but it's rad to have all of those calculations that Jofwu did in one place like this.

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On 2/15/2018 at 3:05 PM, king of nowhere said:

This makes me think. The size of roshar continent is roughly that of asia, and the distance between shinovar and alethkar roughly the one between europe and china. So maybe there was on roshar a Cristopherin Chiken who, after miscalculating the distance involved, attempted to reach alethkar from shinovar sailing westward.

there was no continent to discover, and he sunk in a highstorm anyway.

Isn't that basically the story of the Wandersail?

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On 2/15/2018 at 1:05 PM, RShara said:

Gravitational acceleration isn't directly proportional, I don't think?  So .7 Earth Gravity wouldn't necessarily be 70% of 9.8 m/s^2.  I can't remember for sure.  Anyway, the post above gives the mass of Roshar, which will allow him to calculate the correct gravitational acceleration.

It is. The post above uses the given 0.7g surface gravity to calculate the planetary mass.

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2 hours ago, digitalbusker said:

It is. The post above uses the given 0.7g surface gravity to calculate the planetary mass.

Hmmm.  Weird.  I thought it followed the inverse square law.

 

On 2/15/2018 at 9:58 AM, Shqueeves said:

Gravity on Roshar is .8 that on earth

.7 :P

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3 hours ago, RShara said:

Hmmm.  Weird.  I thought it followed the inverse square law.

It does, but the acceleration we refer to as g is the calculated value at sea level. (Or rather at the defined planetary radius.)

Edited by digitalbusker
Preemptively self-pedantic
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@RShara the only knit-pick I have with your data, which is astonishingly complete, is that I would add the caveat that the weird precession in Roshar's moons is ultimately due to the fact that Roshar (the planet) exhibits an unstable orbit with its nearby bodies.

In other words, in the future, be it distant or near, one or more of Roshar's moons will either slam into its surface, or be ejected from orbit unless something very drastic happens.  Many Cosmere fans forget this fact when first attempting to make orbital projections about Roshar; I can't recall the location of the link off-hand, but I believe Peter has stated this outright in the past.

This assumption leads to a very deep rabbit hole of Lagrange points and stable orbits that really just isn't applicable; I wish you all the best in developing better calculations than your predecessors; TLR knows I didn't get very far...

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14 minutes ago, hwiles said:

@RShara the only knit-pick I have with your data, which is astonishingly complete, is that I would add the caveat that the weird precession in Roshar's moons is ultimately due to the fact that Roshar (the planet) exhibits an unstable orbit with its nearby bodies.

In other words, in the future, be it distant or near, one or more of Roshar's moons will either slam into its surface, or be ejected from orbit unless something very drastic happens.  Many Cosmere fans forget this fact when first attempting to make orbital projections about Roshar; I can't recall the location of the link off-hand, but I believe Peter has stated this outright in the past.

This assumption leads to a very deep rabbit hole of Lagrange points and stable orbits that really just isn't applicable; I wish you all the best in developing better calculations than your predecessors; TLR knows I didn't get very far...

Hey now, it's not my data ;)  I wish my brain worked well enough to come up with that.  I mean I could...but it would involve hours and hours of finding the right equations, paper, and pencils.  My physics classes were a LONG time ago, and while I remember the concepts pretty well, a lot of the technical equations have been erased from my memory! 

The credit goes to jofwu and a few others.  Also, they have worked on the moon issue, and they agree that the moons are super screwy.

Here is the first portion, that doesn't involve OB spoilers.

Here is the second portion that involves OB spoilers.

 

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